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Recent in vitro Models for the Blood-Brain Barrier
Published in Carla Vitorino, Andreia Jorge, Alberto Pais, Nanoparticles for Brain Drug Delivery, 2021
João Basso, Maria Mendes, Maria Ferreira, João Sousa, Alberto Pais, Carla Vitorino
As previously mentioned, microfluidic models are extremely versatile and may also contemplate the culture of other cells of the neurovascular units, thus representing a more reliable physiological state. Astrocytes are star-shaped glial cells which perform different tasks in the CNS, including the biochemical support to the endothelial cells, the secretion of cellular growth substances (growth factors, cytokines and ECM proteins) for the BBB function and assistance in the transport regulation across the capillaries. The close contact with endothelial cells suggests that astrocytes are crucial for the development of BBB, and their differentiation is linked with the BBB maturation. Pericytes are found in the walls of the capillaries and are essential to the control of blood flow in cerebral vessels. Pericytes synthesise elements necessary for the differentiation of the BBB as beta-type platelet-derived growth factor receptor (PDGFRb) and the proteoglycan neural/glial antigen 2 (NG2). Neurons are the main component of the brain and are in direct contact with endothelial cells and astrocytes. They are accountable for the degree of BBB permeability and the control of blood flow, as the presence of neurons increases the barrier effects. Microglia are innate immune cells in the CNS and have an important role in maintaining the function and the integrity of the BBB. For example, the activation of macrophages is one of the marks of an infected brain and suggests that the effectiveness of the barrier is compromised.
Computer-aided Diagnosis (CAD) System for Determining Histological Grading of Astrocytoma Based on Ki67 Counting
Published in Varun Bajaj, G.R. Sinha, Computer-aided Design and Diagnosis Methods for Biomedical Applications, 2021
Fahmi Akmal Dzulkifli, Maryam Ahmad Sharifuddin, Mohd Yusoff Mashor, Hasnan Jaafar
Generally, brain tumors can be divided into two categories. These categories are known as primary brain tumors and metastatic brain tumors [7]. The primary brain tumor is defined as a tumor originally derived from the neoplastic cells of the brain. A metastatic or also known as a secondary brain tumor is a tumor that begins to develop elsewhere in the body and then spreads to the brain to form a new tumor. A primary brain tumor can be divided into two types: glioma and non-glioma. A glioma tumor is a tumor that grows from a glial cell. Glial cells act as supportive tissues in the brain, and they are responsible for providing support and protection for the neurons. Astrocytes, oligodendrocytes, ependymal cells, Schwann cells, satellite cells, and microglia are examples of supporting tissues in the brain [1]. Examples of glioma tumors include astrocytoma, oligodendroglioma, ependymoma, and brain stem glioma. Non-glioma tumors are tumors that form and arise from cells within the brain that are not glial cells. Examples of types of non-glioma tumors are meningioma, medulloblastoma, craniopharyngioma, and pineal gland and pituitary gland tumors.
Propagation of the Action Potential
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The solution, in the form of myelinated axons, is ingeniously simple and highly effective. The axon is surrounded by a myelin sheath consisting of up to 200 layers or so of passive cell membrane interrupted at regular intervals in what are referred to as the nodes of Ranvier (Figure 4.7). The region between adjacent nodes is the internode, whose length is roughly 100–150 times the axon diameter and ranges in length between about 200 µm and 2.5 mm, depending on axon diameter. The sheath is wrapped around the axon during embryonic development by specialized satellite cells of the nervous system – the glial cells (Section 1.2.3). In the central nervous system, the glial cells that form the myelin sheath are referred to as oligodendrocytes, with each oligodendrocyte forming one internode of myelin for up to about 50 adjacent axons. In the peripheral nervous system, a glial cell referred to as a Schwann cell forms one internode of only a single axon.
The effect of the properties of cell nucleus and underlying substrate on the response of finite element models of astrocytes undergoing mechanical stimulations
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Fatemeh Atashgar, Mehdi Shafieian, Nabiollah Abolfathi
Cells of the central nervous system (CNS) include neurons and glia cells (Astrocytes, microglia, and oligodendrocytes) (Castellani and Schwartz 2020), and among them, Astrocytes are of great importance because they play a critical role in the function of the CNS under normal or injury conditions. Astrocytes are involved in the synapses’ formation, maturation, and elimination. They also take part in stabilizing ions, clearing neurotransmitters, regulating extracellular space, controlling neuronal metabolism, regulating the function of the blood-brain barrier and regulating synaptic transmission (Burda et al. 2016; Vasile et al. 2017; Martin-Jiménez et al. 2019; Michinaga and Koyama 2019). In addition, Astrocytes respond to brain damage and infection (for example, during COVID-19 infection) through morphological, metabolic, and cellular changes to maintain brain health (Arévalo et al. 2011; Tremblay et al. 2020). Consequently, evaluating the biomechanical properties of neuronal cells, such as Astrocytes, is the primary step in developing multiscale models and investigating brain damage (Bernick et al. 2010).
Reactive astrogliosis in the dentate gyrus of mice exposed to active volcanic environments
Published in Journal of Toxicology and Environmental Health, Part A, 2021
A. Navarro, M. García, A.S. Rodrigues, P.V. Garcia, R. Camarinho, Y. Segovia
Air pollution affects the brain through different paths including molecular, cellular, and inflammatory (Genc et al. 2012). The toxic gases and other air contaminants induce the production of proinflammatory cytokines that reach the CNS through the brain–blood barrier (BBB) or directly through the olfactory epithelium. These neuroinflammatory processes trigger a response in the brain glial cells, which constitute the immune system in the CNS. Astrocytes, the most abundant glial cell type of the CNS, are responsible for (1) maintaining brain homeostasis, (2) providing metabolites to neurons, (3) synapses monitoring, (4) regulating the extracellular balance of ions and neurotransmitters, and (5) taking part in BBB maintenance and permeability (Sofroniew 2009). Astrocytes are immunocompetent cells and therefore, respond to CNS injuries by activating and producing cytokines or initiating the immune adaptive responses (Cordiglieri and Farina 2010; Farina, Aloisi, and Meinl 2007). Certain cytokines, such as tumor necrosis factor alpha (TNF α), ciliary neurotrophic factor (CNTF), or interleukin 6 (IL-6) induce astrocytic activation. This activation is not a single none-or-all response, but a multifaceted process involving modifications in gene expression and cell morphology. Astrocytic activation is controlled in a time- and context-dependent way, which indicates that this process might play a beneficial role but might also lead to harmful effects.
A Functional BCI Model by the P2731 working group: Physiology
Published in Brain-Computer Interfaces, 2021
Ali Hossaini, Davide Valeriani, Chang S. Nam, Raffaele Ferrante, Mufti Mahmud
The brain also contains a range of cells that support its electrical, biochemical and metabolic functions. Collectively known as glia, these cells support, protect, nourish and insulate neurons, and they are essential for proper cognition as well as health. The primary categories of glial cells are microglia, astrocytes, oligodendrocytes and NG2-glia progenitor cells. Oligodendrocytes are essential to the operation of the brain as an electrical organ because they act as insulators when signals are propagating through axons [34].